When I blogged recently about Microsoft’s plans on the operating-systems front following Windows 8.1, I mentioned a couple of “spring 2015” releases. It turns out the Microsoft codename for that wave of deliverables is “Threshold.” A couple of my contacts have confirmed that Microsoft Executive Vice President Terry Myerson recently mentioned the Threshold codename in an internal email about plans for his unified operating-system engineering group. If all goes according to early plans, Threshold will include updates to all three OS platforms (Xbox One, Windows and Windows Phone) that will advance them in a way to share even more common elements. (The codename Threshold, for those wondering, derives from the planet around which the first halo ring orbited in the original Halo game launched back in 2001. Threshold joins “Cortana,” Microsoft’s answer to Siri, as yet another codename with its origins in the Xbox franchise.)